Process for the manufacture of steel and the fixation of nitrogen



Aug. 19 1924. ,505,28l

A. NAGELVOORT K Paooss FOR THE MANUFACTUHE oF STEEL A ND THE Fxmzow oFNITROGEN Filed may 25. 1921- Patented Aug. 1e, 192.4.

UNETED STATES PATENT OFFICE.

ADRIAAN NAGELVOORT, OF PROVIDENCE, RHODE ISLAND, ASSIGNOR TO THE NITRO-GEN CORPORATION, OF PROVIDFESE, RHODE ISLAND, A CORPORATION F RHODEISLAND.

PROCESS FOR THE MANUFACTU'RE OF STEEL AND THE FIXATION OF NITROGEN.

Application filed May 25. 1921.

To all whom t may con-cern.'

-Be it known that I, ADRIAAN NAGEL- vooRT, a citizen of the UnitedStates, residing at Providence, in the county of Providence and State ofRhode Island, have invented certain new and useful Improvements inProcesses for the Manufacture of Steel and the Fixation of Nitrogen, ofwhich the following is a specification.

This invention relates to an improved process for the manufacture ofsteel and the fixation of nitrogen, and comprises certain novel stepsand combinations of steps adapted to facilitate the removal ofimpurities present in the iron and at the same time effect the formationof cyanogen compounds thus enabling the manufacture of steel to becarried out efiiciently from iron which is not readily adapted for useunder processes heretofore employed, and at the same time permit therecovery of valuable byproducts whereby the cost of the operation may bematerially reduced.

One object of my invention is to provide an improved process for themanufacture of steel. which may be utilized in effecting thepurification of iron containing a high sulfur or phosphorus content,whereby such iron may be used in the manufacture of steel as readily asiron containing little or no sulfur and phosphorus which is nowconverted into steel by means of the Bessemer process.

Another object of the invention is to pro- Vide an improved processwhereby the carbon removed from the metal in the manufacture of steelmay Ibe combined with nitrogen to form a cyanogen compound and recoveredas a valuable by-product, either when treating iron obtained from oreshaving a high sulfur phosphorus content or when used in treating ironobtained from ores sufficiently free from sulfur or phosphorus to renderthem capable of use in the production of steel by the Bessemer process.

Other objects of the invention comprise the use of certain steps andcombina-tions of steps in the effectuation of the process as will bemore fully disclosed in the detailed description to follow.

Serial No. 472,554.

In the manufacture of steel by the wellknown Bessemer process asheretofore employed, the crude or pig iron is melted and placed in aBessemer converter in a molten condition, when a current of air isforced through the molten metal to oXidize the silicon and carbonpresent in the metal, the gaseous combustion products resulting from theoxidation of the impurities mentioned escaping from the converter. Incarrying out the Bessemer process as above described.l the air is forcedinto the base of the converter under pressure, through a plurality ofopenings or tuyres, and passes upwardly through the molten mass intointimate contact with all portions of the metal, the oxygen present inthe air reacting with the inipurities named t-o form combustion productswhich escape from the top of the converter. In effecting thepurification of the molten metal as above described, considerable heatis evolved by reason of the strongly exothermic reaction resulting fromthe oxidation of the silicon and carbon present in the mass. IVhile themolten metal is usually subjected to the air blast for from to minutesin order to effect complete or substantially complete removal of thesilicon, and carbon, from 2 to 4L minutes usually suffices t-o effectthe removal of the silicon present in the mass, the remainder of theAperiod of treatment being devoted to the removal of the carbon. A

`While the above described process has come into extensive use and iswell adapted for the treatment of certain grades of iron, forexample,those which contain little or no plosphorus, it is not adaptedfor use in the treatment of iron containing any appreciable quantity ofphosphorus which iron must, at the present time, either be utilized fo-rmaking cast iron or be converted into steel by the so called basicprocess which is comparatively expensive.

In United States Patent No. 1,174,944 granted vto John E. Bucher March7, 1916 a method of fixing nitrogen is described wherein a bath ofmolten metal, such as iron, is saturated with carbon, and nitrogen gas1s, together with a metallic vapor such as scdium forced into the moltenmass to effect the fixation of nitrogen by reason of the affinity ofnitrogen for carbon in the presence of an activator,such as the molteniron, and an alkali metal.

In this patent'the main object of the invention is the fixation ofnitrogen, and means is provided for maintaining the molten metalconstantly saturated with carbon .'by forcing carbon into the metal tomaintain a constant supply of free carbon thereln 1n addition to thegraphitic and combined carbon normally present in the iron.

It is my purpose to utilize certain of the principles set forth in theabove mentioned patent to provide a somewhat different method ofoperation particularly adapted for use in connection with the productionof Y steel, whereby cyanogen compounds may be formed and recovered asvaluable by-products in the manufacture of steel, and the process madeavailable for use not only with iron obtained from ores free orsubstantially free from sulfur or phosphorous but also with ironcontaining such a large percentage of sulfur or phosphorous as wouldordinarily Irender the same incapable of use for the manufacture ofsteel by the Bessemer process.

In one method of carrying out my 1mproved process I may make use of theordinary Bessemer converter provided with a suitable re-proof lining,and mounted upon `trunnions in the usual manner. A't the 'base of theconverter is the usual alr chamber communicating with the interlor ofthe converter through a plurality of openings or tuyres. The moltenmetal may be placed in the converter in the usual manner, and subjectedto an air blast for forclng air from the air chamber through the tuyresinto the molten metal to remove certain impurities therefrom, such assilicon. Since the reaction between the silicon and the oxygen ofthe/air is strongly exothermlc, a considerable degree of heat is evolvedduring the oxidation of the silicon as above describedv which serves toraise the temperature of the molten metal, and thus promote thereactions which will be hereinafter described. As the silicon in thecrude iron is the first of the various impurities present therein to beremoved by the air blast, and since from two to four minutes usuallysuffices for its removal, I purpose to employ the air blast as abovedescribed only for such tlme as is necessary to remove or Substantiallyremove the silicon, when I cut off the supply of compressed air tothe,air chamber at the base of the converter, and simultaneously connectthe air chamber with a supply of nitrogen maintained under sufcientpressure to force the same through the tuyres and into the molten massin a similar manner to that in which air is forced therethrough by theair blast. During the period that the nitrogen blast is in operation, Ipreferably introduce an alkali metal, such for example, as sodium, intothe converter with the nitrogen to assist both in the reaction betweenthe nitrogen and carbon of the molten iron and also to combine with thesulfu-r, or phosphorus or both present in the iron and form with theseelements compounds which may be readily eliminated from the mass.

The alkali metal serves to promote the reaction between the carbon andnitrogen to form cyanogen compounds and also, being stronglybasic,'reacts with the sulfur and phosphorus present in the iron to formcompounds capable of being readily eliminated.

The gaseous products of the reaction resulting from the nitrogen blastmay be conducted from the converter through cooling pipes or chambers toscrubbing towers where they are washed with water or puri- 'fyingsolutions to recover the cyanogen compounds formed. In order tofacilitate the separation and recovery of the gaseous products formed bythe reaction between the nitrogen and the molten material it isadvisable to either provide the converter with a hood communicating withthe cooling chambers and so formed that it may be opened to permit theescape of the gases formed during the air blast and closed to conductthe gaseous products of the nitrogen blast to said chambers, or theconverter may be movably mounted and so positioned that during the airblast the gaseous product formed therein may escape, while allowing theconverter to be swung yinto position beneath a suitable hood just iprior to the commencement of the nitrogen blast-to conduct the cyanogencompounds formed by reaction with the nitrogen into the coolingchambers. The cyanogen compounds of the reaction which itis desirable torecover comprises cyanogen and alkali metal cyanids, and although thesecyanogen bearing gases as they pass from lthe converter may be mixedwith certain other gases, they are capable of being readily separatedtherefrom in passing through the cooling chambers.

As stated, the silicon content of the iron is removed or substantiallyremoved by the air blast, and the nitrogen supplied to the metal duringthe nitrogen blast reacts with the carbon present therein at the hightemperature of the metal to form cyanogen or passage of the metalthereto. The heat of the converter willbe sufficient to liquefy thealkali metal and enable it to reach the tuyres while contact with themolten mass will immediately convert it to a vapor.

This process contemplates preferably the use in a Bessemer converter, ormodified form of Bessemer converter, of pure nitrogen made byliquefaction of air, the oxygen content of which may be advantageouslyused in a blast furnace to enrich the air blast: If the oxygen isemployed in a blast furnace an increased yield of pig iron will resultby reason of the elevated temperature at the tuyres.

The nitrogen readily unites both with the graphitic carbon and thecombined carbon present in the iron to form cyanogen compounds at thetemperature to which the molten vmass is raised by reason of theoxidation of the silicon.

As an alternative method of carrying out the invention I may useproducer gas, or any gaseous mixture the main constituents of which arenitrogen and hydrogen, as a substitute for the purenitrogen gasmentioned above as preferably used in the nitrogen blast, in which casethe gaseous products are cooled and passed through scrubbing towers torecover the cyanogen and cyanogen compounds in the same manner as hasbeen previously described. However, when producer gas is substituted forpure nitrogen the alkali metal previously mentioned should not be usedsince alkali metal cyanids break down in the presence of CO and CO2 athigh temperatures to form carbonates thus preventing the recovery of thenitrogen in the form of cyanogen compounds. If, however, a gaseousmixture containing nitrogen andx hydrogen is used in which CO and CO.,are not prent the alkali metal may be used in conjunction therewith forassisting in the cyanogen forming reaction.

The hydrogen gas present in the producer gas or the gas mixturedescribed will act as ay basic element in place of the alkali metal toform gaseous compounds such as sulfuretted hydrogen and phosphorettedhydrogen with the sulfur and phosphorus content of the iron, while thecyanogen resulting from the reaction between the nitrogen and carbonwill pass off as cyanogen or hydrocyanic acid. While it is preferable tomaintain as low a percentage of carbon monoxid and carbon dioxid aspossible in the gases used for the nitrogen blast, the presence of asmall percentage of gaseous hydrocarbons therein exerts no deleteriouseffect, but their l presence on the contrary tends to increase the yieldof cyanogen compounds since they serve to increase the quantity ofcarbon capable of uniting with nitrogen.

As an example of one form of apparatus which may be employed in carryingout my Bessemer converter of the conventional type,'

having a metal shell 2, a suitable heat resistant lining 3, and.provided with trunnions 4 and 5 projecting outwardly from the metalshell 2 for mounting in bearings 6 and 7 respectively, the bearingsbeing each supported by a suitable base frame 8.

The converter is provided with the usual Vmouth 10, and tuyres 11 formedin the baseof the converter to place the interior thereof incommunication with a passage 12 formed in the base thereof. rlhe bearing6 is provided with a bore 14 communicating with the interior thereof andwith a passage 15 formed in the trunnion 4, while a pipe 16 is securedto the bearing 6 in anydesired manner and communicates with the bore 14and the passage 15 formed in the trunnion 4.

A pipe 17 connects the passage 15 in the trunnion 4 with the passage 12in the base of the converter, and a receptacle 18 may be supported fromthe converter body or the pipe 17. The receptacle 18, which serves as acontainer for the alkali metal may be provided with a removable cover19, and has an out-let 20, communicating with the pipe 17. When foundnecessary or desirable any suitable means may be employed for forcingthe alkali metal in the receptacle 18 into the connecting pipe 17. Thebearing 7 is provided with a bore 21, communicating with the interiorthereof and with a passage 22 formed in the trunnion 5, while a pipe 24is secured to the bearing 7 in any suitable or desired manner andcommunicates with the bore 21 and the passage 22, all of which parts aresimilar to those previously mentioned in connection with the bearing 6and trunnion 4. A passage 22 with the passage 12 in the base .of theconverter. Suitable stutling boxes may be provided in the bearings 6 and7, as is obvious to one skilled in the art, and any suitable or desiredmeans for making the connections between the pipes 16, 17, 24 and 26 andthe bearings, trunnions and converter, may be employed as conditions mayrequire.

A hood 27 is secured to a pipe section 28, which is in turn connected bya hinge joint 29 to a pipe 30, and adapted to be swung 4downwardly overthe mouth 10 of the converter or swung upwardly therefrom in order toreceive the gaseous products' given off from the converter or permit theescape of such products as desired.

The pipe 30 enters the base of a scrubbing pipe 26 connects the tower 31to convey selected gaseous products from the converter to the scrubbingtower where they may me contacted with certain reagents admitted to thetower through the pipe 32, the products resulting from contact of thegaseous products with the reacting agents being removable through thepipe 33 or by other suitable means. The pipe 35 is provided forconveying the 'gaseous products remaining after treatment in thescrubbing tower to a second tower for further treatment or to anydesired point for further utilization.

In carrying out my improved process by means of the apparatus shown,when the converterl has\received its required charge of molten metal,air is forced in lthrough the pipe 24 arid the air blast is maintainedfor a suiiicient time to remove or substantially remove the siliconcontentof the metal and raise the temperature thereof to the requireddegree. During this portion of the operation the hood 27 is raised topermit the escape of the gaseous products given olf from the converter.When this portion of the operation has been completed the supply of airthrough the pipe 24 is shut olf and nitrogen gas, or its equivalent asstated, is admitted through. the pipe 16 and forced through the moltenmetal in the converter. Immediately upon the commencement of thenitrogen blast,or as soon thereafter as the gaseous reaction productsresulting from the union ofthe nitrogen with the carbon content of themetal are given olf in the required degree, the hood 27 is lowered overthe mouth of the converter and the gaseous products conveyed through thepipe 30 to be admitted suitably cooled to the base ofthe tower 31. Whennitrogen alone is admitted through the pipe 16, the requisite quantityof akali metal contained in the receptacle 18 is permitted to passthrough the outlet 20 int-o the pipe 17 and'- be carried along by thenltrogen blast into the molten metal.

U When the above described process is carried out either by using purenitrogen gas in the presence of an alkali metal or by the use ofnitrogen gas in the presence of hydrogen, the nltrogen unites with thecombined and gr'aphitic carbon of the iron to form cyanogen `compoundswhich pass off as gases and are recovered as by-products either ascyanogen compounds or as derivatives thereof. The alkali metal orhydrogen act' as baslc elements uniting with the sulfur or phosphorus orboth in the iron to form compounds which are eliminated froml the moltenmass during the treatment. The. term basic element as used throughoutthe specification and claims, is employed as embracing either hydrogengas or an alkali metal, either of which acts as a base in uniting withthe sulfur or phosphorus to form a sulfid or phosphid.

The gases obtained by treating the molten mass with nitrogen gas,producer gas, or a gas mixture as described, after being cooled to below800 C. in the cooling chambers, may be treated with steam to formammonia or ammonia compounds, or converted into nitric acid by wellknown methods.

After the removal from the molten iron of the impurities mentioned, anydesired grade of steel may be obtained by the addition of suitableproportions of metallic alloys as is the usual practice in themanufacture of steel by the Bessemer process.

Throughout the specification and claims the term iron is employed todesignate generally the crude iron commonly known as pig iron in thecondition of partial puriication in' which it exists after being removedfrom the blast furnace, and before being subjected to further treatmentby the Bessemer, open Ahearth or other method of treatment employed forconverting the same into steel. While pig iron containing a certainpercentage of sulfur may be used 1n the Bessemer process, this processwill permit the use of iron containing ahigher sulfur content than canbe ordinarily used in the Bessemer process. Iron such as is ordinarilytreated by the open hearth process may be used in carrying out theprocess herein described.

In order to prevent circumlocution in the specification and claims theterm cyanogen compounds has been generally employed in designating thecarbon-nitrogen products resulting from the reaction between nitrogenand carbon in the molten mass. It is to be understood, however, thatthis term has been used to designate generally not only cyanogencompounds of alkali metals and other basic elements, but also cyanogengas which under certain circumstances may be included in the products ofthe said reaction. Although I have described in considerable detailcertain precise steps and sequence of steps which I have found itdesirable to employ as well as certain particular substances andcompounds which I have found to be eiiicient in use, in order to makeclear to those skilled in the art one method of practicing theinvention, it is to be understood that Ido not desire or intend to belimited to the precise materials designated as preferred nor the exactsteps or sequence of steps indicated as` preferred except `as the samema fol owing claims when broadly construed in the light of my invention.

Having described my invention, what I claim is:

1. The process for forming steel from molten iron which comprises,subjecting the 'molten iron to an air blast to removecertain impuritiestherefrom, and then reacting upbe included within the terms of the onsaid iron with nitrogen to effect a union between the nitrogen and thecarbon present in the iron.

2. The process for forming steel from molten iron which comprises,subjecting the molten iron to an air blast to oxidize certain impuritiestherein with evolution of heat, and then reacting upon said iron at theelevated temperature produced by the first reaction with nitrogen tocombine the nitrogen with the carbon present in the iron.

3. The process for forming steel from molten iron which comprises,subjecting the molten iron to an air blast to remove certain impuritiestherefrom, and then reacting upon said iron with nitrogen in thepresence of a basic element to remove carbon therefrom in the form of acyanogen compound.

4. The process for forming steel from molten iron which comprises,subjecting the molten iron to an air blast to oxidize certain impuritiestherein with evolution of heat, and then reacting upon said iron at theelevated temperature produced by the first reaction with nitrogen in thepresence of a basic element to eect the formation of a compoundcontaining carbon and nitrogen.

5. The process for forming steel from molten iron which comprises,subjecting the molten iron to an air blast to remove certain impuritiestherefrom, and then reacting upon said iron with nitrogen in thepresence of an alkali metal.

6. The process for forming steel form molten iron which comprises,subjecting the molten iron to an air blast to oxidize certain impuritiesin the iron with evolution of heat, and reacting upon said iron at theelevated temperature produced by the first reaction with nitrogen in the`presence of an alkali metal.

7. The process for forming steel from molten iron which comprises,removing the silicon content from said iron by oxidation,

and reacting upon the said iron with nitrogen to remove carbon therefromby combining the carbon present in the iron with nitrogen.

8. The process for forming steel from molten iron which comprises,removing the silicon content from said iron by oxidation, and reactingupon the said iron with an alkali metal in the presence of nitrogen toeffect a combination between the alkali metal and the sulphur orphosphorus content of the iron and remove the sulphur or phosphorus fromthe iron.

9. The process for formingv steel from molten iron which comprises,removing the silicon content from said iron by oxidation, and reactingupon the said iron with nitrogen in the presence of a basic element toform a cyanogen compound and effect the removal of the carbon from themetal.

1Q. The process for forming steel from molten iron which comprises,removing the silicon content from said iron by oxidation, and reactingupon the said iron with nitrogen in the presence of an alkali metal toremove carbon and other impurities therefrom.

11. The process for forming steel from molten iron which comprises,removing the silicon content from said iron by oxidation with evolutionof heat, and reacting upon said iron at the elevated temperatureproduced by the oxidation of the silicon content thereof with nitrogento remove carbon therefrom.

12. The process for forming steel from molten iron which comprises,removing the silicon content from said iron by oxidation with evolutionof heat, and reacting upon said. iron at the elevated temperatureproduced by the oxidation of the silicon content thereof with an alkalimetal in the presence of nitrogen to effect a combination between thealkali metal and the sulphur or phosphorus content of the iron andremove the sulphur or phosphorus from the iron.

13. The process for forming steel from molten iron which comprises,removing the silicon content from said iron by oxidation with evolutionof heat, and reacting upon said iron at the elevated temperatureproduced by the oxidation of the silicon content thereof with nitrogenin the presence of a basic element to effecta union of the nitrogen with4carbon contained in the metal.

14. The process for forming steel from molten iron which comprises,removing the silicon content from said iron by oxidation with evolutionof heat, and reacting upon said iron at the elevated temperatureproduced by the oxidation of the silicon content thereof with nitrogenin the presencel of an alkali metal to remove carbon therefrom.

15. The process for forming steel and recovering eyanogen compounds frommolten iron which comprises, subjecting the molten iron to an air blastto remove certain impurities therefrom, effecting a reaction between thecarbon remaining in 'the molten iron, vnitrogen and a basic element toform a cyanogen compound, and recovering theV cyanogen compound. f

16. The process for forming steel and recovering cyanogen compounds frommolten iron which comprises, subjecting the molten iron to an air blastto remove certain impurities therefrom, effecting a reaction between thecarbon remaining in the molten iron, nitrogen and an alkali metal toform a cyanogen compound, and recovering the cyanogen compound.

17. The process for forming steel and recovering cyanogen compounds frommolten iron which comprises, removing the silicon content from said ironby oxidation, effect'- ing a reaction between the remaining carboncontent of the iron, nitrogen and a basicl element to form a cyanogencompound, and recovering the cyanogen compound.

18. The process for forming steel and recovering cyanogen compounds frommolten iron which comprises, removing the silicon content from sadion byoxidation, eiecting a 'reaction between the remaining carbon content ofthe iron, nitrogen and an alkali metal to form a cyanogen compound, andrecovering the cyano en compound.

In `testimony whereof have aixed my signature.

ADRIAAN AGELVO ORT.

